The largest and first quad core iMac takes the stage. (November 14th, 2009)

The 27-inch iMac is already a milestone for Apple through its inclusion of a truly greater-than-HD display, but the addition of Core i5 and Core i7 processors transforms it into a near powerhouse. This is the first iMac in recent memory to come close enough to Apple's workstations that it could replace one of them. Our review of the Core i5-equipped iMac will find out how close it comes to that goal and whether it's a worthwhile option for any other prospective Mac desktop owner.

Ever since the iMac G5 debuted over five years ago, Apple has taken to a surprisingly conservative tack for its all-in-one computer design. The late 2009 iMac shares the same hanging-photo-frame style as its predecessors and inherits all its traits as a result. For the most part, that's a good thing if you're receptive to the integrated concept in the first place. It frees up a considerable amount of desk space, even underneath the display, and allows for a significant amount of display pivoting while still remaining light enough to rotate freely.

Both the 21.5-inch and 27-inch iMacs have notably switched to 16:9 aspect ratio displays and are accordingly wider without being much taller than their old 16:10 equivalents. Besides providing a more natural field of vision -- more on that later -- it has arguably brought about a number of welcome aesthetic and practical changes. Gone are the large "chin," oversized logo and visible frame around the display area. While Apple is still keen to let any visitors know who made the iMac, the new design is subtler. The all-aluminum back may be lifted directly from the LED Cinema Display, but it has the upshot of serving as a heatsink and of reducing the impact of scratches; you're no longer likely to scuff the back because you missed the USB port while plugging in your iPod.

However, the growth of the iMac has had an unpleasant side effect on the 27-inch model: it's big. So big that it will push many of the items on your desk to the side and is less likely to fit in cubbyholes where even the 24-inch model might have had a chance of fitting. It's heavier, too. Many of its likely target audience won't mind as they'll be using relatively large, flat desks, but be sure to measure any tight space before you go shopping.

Expansion on the new iMac has mostly taken a turn for the better. By far the most conspicuous addition is an SD/SDHC card slot just underneath the optical drive. While it may disappoint pros that might want to load in CompactFlash, the average owner or even those with entry-to-mid-range DSLRs can now load photos without having to occupy a USB port either for a card reader or the camera itself. In our experience, it was fast enough to make offloading significant batches of photos relatively quick.

Most of the expansion on the back is the same and is adequate, though not spectacular. The four USB ports may run under the six, eight or more ports found on many Windows desktops, but this is now more forgivable with a Bluetooth mouse and keyboard as standard. Other changes are primarily tweaks rather than overhauls. FireWire 400 has disappeared and will push those with legacy devices to get an adapter, but we're now at the point where many external hard drives, video cameras and even CompactFlash card readers now virtually need the full speed of FireWire 800.

The Mini DisplayPort (mDP) connection notably now works as a video input, though this isn't quite the revolution it seems to be. To use it as a display for a game console or for a computer without its own native jack, you'll need a DVI-, HDMI- or VGA-to-mDP input adapter that doesn't exist as of press time. Until then, the connector will mostly be useful for owners of unibody MacBooks and MacBook Pros that want to temporarily borrow the iMac's screen.

Heavy duty users will be pleased to know that RAM expansion has finally moved beyond two slots. The larger iMac can take up to 16GB of RAM and, more importantly, has two RAM slots free. Although they're still notebook-sized (SODIMM) slots and will cost you more to upgrade on average than desktop slots, you now don't have to replace any of the standard memory sticks to jump to 8GB or even 12GB of RAM. Graphics and video editing professionals now finally have an iMac with enough memory headroom to accommodate their needs.

If there's an annoyance in the design, it's the same lack of hard drive access or front/side ports that has affected the iMac for years and has been the subject of criticism from Windows converts. This does make plugging in more storage, a portable device or a peripheral less convenient. All the same, the sheer amount of wireless in the iMac, along with the ease of spinning it around, has reduced the weight of those gripes. Just be aware of your local Mac-certified repair shop in the event your hard drive dies.

the 27-inch display

Undoubtedly, the attention-getter of the new iMac is the 27-inch model's namesake massive display. Being both large and now 16:9, it can almost completely fill your forward view and is decidedly better for widescreen movie viewing as you'll see less of the black bars that come from cropping a non-native video size. HD video is simply exceptional on this display; we could easily see many apartment dwellers giving up their TVs entirely in favour of the larger iMacs, at least if they don't mind having to replace their TV when the computer inside it becomes obsolete.

And unlike other all-in-ones at or near the same size, Apple's system isn't just magnifying an existing display resolution. The 27-inch panel produces a 2560x1440 image -- essentially, a 30-inch Cinema HD Display with some of the vertical space clipped off. In practice, it amounts to a tremendous gain in usable screen area over the outgoing 24-inch model. It's now possible to fit at least two full web pages side by side while still having room for a chat window; pro apps like Aperture, Final Cut or Photoshop can work with material closer to its actual resolution; and even home apps like iMovie or iPhoto get more room to breathe. There's additionally a certain thrill to playing 1080p video in windowed mode and still seeing most of the desktop free for other tasks.

Image quality is thankfully at least as good as before and, if anything, has become even better. Both sizes of iMac now use IPS (in-plane switching) LCDs instead of cheaper PVA (patterned vertical alignment) or TN (twisted nematic) panels found on most computer displays. Users of 24-inch iMacs will already know this experience well, but the end effect for the entire line is to get exceptionally rich colors and wide viewing angles. Brightness and absolute color accuracy does appear to drop off, but only at extreme perspectives that wouldn't be useful for work. In the right lighting environment, we'd seriously consider the iMac for color proofing in still image editing or a video production tool like Final Cut Studio's Color.

LED backlighting should make this even better, as it prevents the light from getting dim at the edges of the screen and ensures uniform color across the entire panel. To be honest, we'd never really noticed a vignetting effect on a 24-inch iMac, either. Even so, it does mean that the larger 27-inch panel won't risk that effect either. There's likewise the positive side-effect of lowered power consumption compared to a fluorescent display at the same size, not to mention fewer toxic chemicals to hurt the environment at the end of the computer's lifespan.

As with the previous aluminum iMac, the only real flaw left is the glossy, all-glass finish over the display. It's true that it's easier to clean and produces more visibly vibrant color than a matte display. Simultaneously, though, it also means that the iMac has to be placed properly to avoid lighting elements reflecting off the screen and ruining the image. We've had success with our iMac and have quickly grown used to what glare is left, but we wish Apple would take a cue from its changes to the MacBook Pro line and give the option of a matte finish for pro workers that may not have the luxury of controlling ambient light.

cord-free: the Magic Mouse and wireless keyboard

If you don't custom-order the iMac online, your input for the iMac will come solely through the latest incarnations of Apple's Bluetooth keyboard and mouse combo. The wireless keyboard will seem the most familiar as it's the exact same peripheral that appeared along with the first aluminum iMac in 2007. Its compact nature is a mixed bag. It's excellent for freeing up space and is just as comfortable as any modern MacBook keyboard -- that is to say, very. But those who want full-size Command, Control and Option keys, or who want a number pad, will still miss getting a full-length set as standard, which they did until spring of 2009.

The Magic Mouse is more polarizing. It seemingly accomplishes Apple's goal of eliminating any (visible) buttons entirely and, to some extent, recreates the input of the MacBook line's glass trackpad in desktop form. Like with the Mighty Mouse, it still depends on one physical button for both left- and right-click actions. Everything else, however, is controlled through touch input, and both the trackball as well as the "squeeze" button have vanished.

This works surprisingly well. We miss having extra buttons to assign to tasks like Dashboard, but scrolling is now much easier. It's now possible to scroll with a much wider variety of speeds, including very fast momentum scrolling: flicking quickly multiple times can rapidly fly through a long page or document. Apple's new mouse is the only one we've seen outside of Logitech's MX and VX lines to do this, and it does so with the horizontal freedom Logitech misses and without the clog-prone scroll ball that affects the Mighty Mouse. The multi-touch system Apple uses is intelligent enough to recognize your palm and also supports handy, though not essential, two-finger page navigation functions.

Despite the ultra-low profile needed to make multi-touch work on the mouse, we found it increasingly comfortable the more we used it. Whether you agree may depend entirely on the size of your hands and the height of the mouse relative to your desk.

We wouldn't call this a uniform victory, though, and most of the drawbacks come from the inherent nature of Bluetooth. By going cordless out of the box, Apple now requires that most iMac owners carry a supply of spare batteries for when the mouse and keyboard run low on power in several months' time. They're also hindrances in Boot Camp mode. While it's possible to get both working fully in Windows, they won't be completely auto-paired as they are in Mac OS X and seem more prone to slight input skips in Microsoft's platform due to interference. Anyone who boots regularly into native Windows (virtual machines are excepted) should strongly consider ordering an iMac with the wired keyboard and mouse set, which mercifully don't cost extra.

performance: subjective tests

Intel's decision to emphasize efficiency over clock speed has created an interesting problem for system builders like Apple; it now can't really use escalating numbers to differentiate its various computer models. The Core 2 Duo iMacs have a nominally higher 3.06GHz clock speed, but in most cases they'll lose out to the numerically "slower" Core i5 and i7 models due both to the two extra processor cores and the various tricks Intel uses to optimize the amount of work done in a given cycle. Turbo Boost is the biggest aid. Our Core i5 may only run at 2.66GHz normally, but it can ramp up to 3.2GHz when one or more of the cores aren't needed. In theory, it has all the benefits of quad-core without being punished by lower clock speeds.

That bears out in our tests. Perhaps the greatest allure of a quad-core iMac is just ability to juggle multiple tasks at once without flinching. While these are partly disk- and storage-intensive, it's possible to launch and run several apps simultaneously without noticing a tangible drop in their load times or responsiveness. We'd still advise against running more than one time-dependent task at once, but if necessary an iMac can now easily handle video encoding or a similarly tough task without noticeably bogging down everything else.

If anything, average users may actually struggle to eke as much as they can out of the quad-core chip using current software; it's enthusiasts and professionals who will get the most out of it as creative apps and games see the most visible gains.

To that extent, we tested gaming both in Mac OS X and in Boot Camp with Windows 7 -- which, as much as some Mac users may dislike to admit, is the most likely gaming environment on the new iMac. Here, the Core i5 along with the Radeon HD 4850 (actually a Mobility Radeon part) results in an iMac that can actually participate in reasonably high-end gaming. Titles like Heroes of Newerth and Left 4 Dead still have a modern level of detail but can run at the system's full 2560x1440 resolution, above 30 frames per second, without having to significantly lower settings outside of antialiasing. Other games like Crysis have to run at lower resolutions like 1600x900 but can still run with all but extreme details left turned on.

There are caveats at present to using Windows on the iMac, but once these are ironed out, the 27-inch iMac may well be the de facto choice for those who want a Mac but are either still tied to Windows or are comfortable returning to it on a regular basis.

performance: benchmarks

Synthetic tests may be the clearest illustration of how much a quad-core processor can help when it's given free rein to run all four cores. As such, we primarily focused on tests where clear differences exist with multiple cores active.

Of these, the clearest example is Maxon's CINEBENCH R10; it checks processor performance in what's close to an actual professional environment while also bringing the video chipset into play. We compared the new iMac against what was one of Apple's best models when the first aluminum iMacs appeared, a 24-inch iMac with a 2.4GHz Core 2 Duo, 3GB of RAM and a Radeon HD 2600 XT, and came back with some of the largest inter-generational performance leaps we've seen. With both running a fully updated Snow Leopard, the Core i5 iMac was already 47.3 percent faster when just one core was active -- the result of both Turbo Boost and higher memory bandwidth -- but over 2.5 times faster when all four cores were invoked. OpenGL graphics performance was faster too as the two generations newer hardware can process much more in parallel.

Other tests showed similar if less dramatic results. GeekBench, which tests processor performance on a more abstract level, approximately doubled performance both overall and in almost all individual categories. We also included Xbench; it's an admittedly aging test that isn't wholly representative, but even here we saw clear benefits in program threading (when all four cores could be active) and in memory performance.

Some tasks won't see increases on these levels, as extra cores either can't be used or will be wasted by programs that don't know how to take advantage of everything that's available. Still, the Core i5 should prove future-ready once more apps start taking advantage of the Grand Central Dispatch feature built into Snow Leopard and its ability to distribute work more equally between cores. Moreover, the iMac we tested isn't the fastest Apple has to offer; a build-to-order 2.8GHz Core i7 model has Intel's Hyperthreading feature and, in the right circumstances, can behave like an eight-core processor with an appropriate boost to performance. We can see some of those debating a Mac Pro for production work opting for an iMac instead.

a word on Boot Camp compatibility

Before trying to install Windows, it should be noted that we got it running outside of the boundaries that Apple currently recognizes. As of mid-November, Apple had pledged Windows 7 support by the end of 2009 but hadn't yet delivered. If you try to load the OS as of today, you can install it but will never properly finish booting: the display simply turns black after the Windows logo splash.

Right now, the only way to get it working is to delete graphics drivers and install new ones; even then, it's also necessary to work on audio and Bluetooth drivers beyond the steps Apple would suggest. Once it works, it works well, but you implement these steps only if you're comfortable with troubleshooting and at your own risk. If you're reading this in 2010 or beyond, though, many of these issues will be gone.

wrapping up

Desktops as the first pick for a computer are gradually becoming a minority. Many don't need the performance of a desktop and just want the small footprint and mobility of a notebook instead. We don't disagree and eventually see a day where all but the heavy lifting is done with a notebook, a point at which the iMac will no longer have relevance.

In the meantime, Apple seems to have found a way to keep the desktop relevant in a notebook era. The 27-inch iMac has a relatively compact footing and can go almost entirely wireless if you like, but it has advantages that simply can't be had in a notebook, whether it's the large display, the support for extra RAM or of course the leap to quad-core. We again see it standing in as a workstation or as a complete media center for those who consider Hulu and iTunes more relevant than Comcast or Time Warner Cable. Even the smaller elements, like the SD card slot, have a practical impact.

Where Apple faces its greatest challenge is simply in convincing others that its priorities are what others would want. For the same $2,000, it's possible to get a faster Core i7-based Windows desktop if you don't mind a big (if expandable) tower and a lower-quality screen. Apple's system is really a mid- to upper-range desktop with an exceptional display, a compact design and ample wireless; if these advantages don't matter to you, no amount of persuasion will convince you the iMac is the better deal. It's a decidedly better proposition than most rival all-in-ones, though. Others as large as the 27-inch Apple system do have advantages like Blu-ray but are obsessed more with narrow-purpose touchscreen apps and TV viewing than working well as a computer.

Also, Apple is partly competing against itself. You can get the screen and all design upgrades for $1,700 if you don't mind a reduced processor and video chipset. Moreover, the "entry" 21.5-inch iMac is now good enough that it can satisfy the majority of users. Its 1080p screen is still the same quality as on the larger model, and you can have the same RAM and storage in a $1,500 trim level. That may be Apple's expectation and a further indication that the highest-end iMac is now a borderline pro system. The 27-inch model is what you get when you have or want to straddle the line between two worlds.

If you fit that definition, or if you simply want the best possible all-in-one desktop, the iMac is still at the front of the pack. We just wonder if Apple can go any further.